"Brian was a family man who adored his grandchildren and family, and had only this week been given the all clear following treatment for cancer.

"Brian and his wife were only just starting to make plans for the future that they only dared to dream of."

Mr Holmes, who lived in Sandy, Bedfordshire, was shopping around 3pm on Saturday when the row broke out.

Shoppers and a first aid-trained manager from Asda went to his aid and he was rushed to Addenbrooke’s hospital in Cambridge but he later died on Sunday surrounded by his family.

Detective Inspector Liz Mead said: "This is an extremely sad incident which has left a family absolutely devastated and our family liaison officers are doing all that they can to assist and support them at this very difficult time.

"I would like to hear from anybody who was in the car park at Asda on Saturday afternoon and may have seen the altercation taking place close to the disabled parking area.

"A number of people have already come forward but it is imperative that we speak with as many people as possible and collect all of the facts into what happened.

"Even the smallest pieces of information could assist us with our inquiries."

The car park has ten disabled bays outside the main entrance of the single-storey supermarket.

An Asda spokesman said: "We are helping the police get to the bottom of what happened.

"Our thoughts are with the gentleman's family during this difficult time."

Both men involved in the row are believed to have had family members with them at the time of the disagreement.

Detective Chief Inspector Tim Redfearn, who is leading the investigation, said it would have been a busy Saturday afternoon when the incident happened and urged anyone who witnessed the argument to come forward.

A post-mortem was set to be carried out yesterday evening or later on today.